Actually, neither will act as vasodilators.
Arginine absorption and further metabolization to NO is too tightly regulated to overcome via oral administration.
Yohimbine is a vasoconstrictor and improves the psychogenic, not organic, milieu necessary to get an erection:
I've used both arginine and yohimbe and have found them both two be useful in sexual performance. I still feel that arginine is an effective vasodilator and nitric oxide booster. And yohimbe is still good at helping one reach a better erection maybe not through vasodialtion, possibly through acting as an aphrodisiac? It does seems that some people may be non responders to yohimbe's effects, but I myself have found success with it in enhancing sexual performance.
"L-arginine transport and nitric oxide synthesis in human endothelial progenitor cells."
ABSTRACT::
Nitric oxide (NO) is an endogenous vasodilator molecule synthetized from L-arginine by a family of nitric oxide synthases. In differentiated human endothelial cells, it is well known that L-arginine uptake via cationic amino acid transporters (y/CAT) or system yL is required for the NO synthesis via endothelial nitric oxide synthase, but there are no reports in human endothelial progenitor cell (hEPC). Therefore, we isolated hEPCs from peripheral blood of healthy donors and cultured them for either 3 (hEPC-3d) or 14 days (hEPC-14d) to characterize the L-arginine transport and NO synthesis in those cells. L-arginine transport and NO synthesis were analyzed in the presence or absence of N-ethylmaleimide or L-nitroarginine methyl ester, as inhibitors of y/CAT system and nitric oxide synthases, respectively. The results showed that L-arginine uptake is higher in hEPC-14d than in hEPC-3d. Kinetic parameters for L-arginine transport showed the existence of at least 2 transporter systems in hEPC: a high affinity transporter system (Km= 4.8 ± 1.1 μM for hEPC-3d and 6.1 ± 2.4 μM for hEPC-14d) and a medium affinity transporter system (Km = 85.1 ± 4.0 μM for hEPC-3d and 95.1 ± 8 μM for hEPC-14d). Accordingly, hEPC expressed mRNA and protein for CAT-1 (ie, system y) and mRNA for 2 subunits of yL system, yLAT1, and 4F2hc. Higher L-citruline production and NO bioavailability (4-fold), and endothelial nitric oxide synthase expression (both mRNA and protein) were observed in hEPC-14d compared with hEPC-3d. Finally, the high L-citruline formation observed in hEPC-14d was blocked by N-ethylmaleimide.
In conclusion, this study allowed to identity a functional L-arginine/NO pathway in two hEPC differentiation stages, which improves the understanding of the physiology of these precursor cells.
Yohimbine treatment of organic erectile dysfunction in a dose-escalation trial.
Abstract
Yohimbine has had questionable effects in men with organic erectile dysfunction. We conducted this study to better define the population of men responsive to yohimbine, because tobacco was thought to affect a regimen of yohimbine more than other risk factors. We measured nocturnal penile tumescence with the RigiScan monitor, hormone profiles, answers to the Florida Sexual Health Questionnaire, and clinical responses at baseline and after two different doses of yohimbine in 18 nonsmoking men with erectile dysfunction. Of the 18 men, nine (50%) were successful in completing intercourse in more than 75% of attempts.
The yohimbine responders were men with less severe erectile dysfunction as manifested by improved increased rigidity on RigiScan testing, higher Florida Sexual Health Questionnaire scores, and slightly higher levels of serum testosterone. Yohimbine is an effective therapy to treat organic erectile dysfunction in some men with erectile dysfunction.
